Solved: Autodelete deltes too many snapshots

cheche030 · ‎2011-05-24

I have a volume with 180 GB and a LUN with 100 GB. The volume has this autodelete settings:

state : on

commitment : try

trigger : volume

target_free_space : 20%

delete_order : oldest_first

defer_delete : user_created

prefix : (not specified)

destroy_list : none

But snapshots are deleted until the volume reaches 98 % capacity. Here is the snapshot history:

First day:

Name	AccessTimeDT	Total
exchsnap__ecorreo__recent	22/05/2011 20:02	997,3
exchsnap__ecorreo_05-21-2011_22.01.24__daily	21/05/2011 20:02	875,7
exchsnap__ecorreo_05-20-2011_22.02.22__daily	20/05/2011 20:03	1628,9
exchsnap__ecorreo_05-19-2011_22.02.14__daily	19/05/2011 20:03	3076,2
exchsnap__ecorreo_05-18-2011_22.02.10__daily	18/05/2011 20:02	2675,6
exchsnap__ecorreo_05-17-2011_22.01.21__daily	17/05/2011 20:02	2882,9
exchsnap__ecorreo_05-16-2011_22.35.32__daily	16/05/2011 20:36	2972,3
exchsnap__ecorreo_05-15-2011_22.02.05__daily	15/05/2011 20:02	2054,8
exchsnap__ecorreo_05-14-2011_22.02.25__daily	14/05/2011 20:03	1308,2
exchsnap__ecorreo_05-13-2011_22.01.20__daily	13/05/2011 20:02	2243,1
exchsnap__ecorreo_05-12-2011_22.01.20__daily	12/05/2011 20:02	1990,5
exchsnap__ecorreo_05-11-2011_22.01.19__daily	11/05/2011 20:02	2144,1
exchsnap__ecorreo_05-10-2011_22.01.16__daily	10/05/2011 20:01	3123,4
exchsnap__ecorreo_05-09-2011_22.01.17__daily	09/05/2011 20:01	2522,1
exchsnap__ecorreo_05-08-2011_22.01.20__daily	08/05/2011 20:02	2668,2
exchsnap__ecorreo_05-07-2011_22.01.22__daily	07/05/2011 20:02	1598,2
exchsnap__ecorreo_05-06-2011_22.01.19__daily	06/05/2011 20:02	2251,7
exchsnap__ecorreo_05-05-2011_22.01.21__daily	05/05/2011 20:02	3889
exchsnap__ecorreo_05-04-2011_22.01.20__daily	04/05/2011 20:02	2987,9
exchsnap__ecorreo_05-03-2011_22.01.20__daily	03/05/2011 20:02	2744,6
exchsnap__ecorreo_05-02-2011_22.01.18__daily	02/05/2011 20:01	2513,7
exchsnap__ecorreo_05-01-2011_22.01.28__daily	01/05/2011 20:02	2164,9
exchsnap__ecorreo_04-30-2011_22.01.21__daily	30/04/2011 20:02	590,7
exchsnap__ecorreo_04-29-2011_22.01.27__daily	29/04/2011 20:02	1481,3
exchsnap__ecorreo_04-28-2011_22.01.19__daily	28/04/2011 20:02	3928,4
exchsnap__ecorreo_04-27-2011_22.01.55__daily	27/04/2011 20:02	4506,8
exchsnap__ecorreo_04-26-2011_22.01.17__daily	26/04/2011 20:01	2181,3
exchsnap__ecorreo_04-25-2011_22.01.27__daily	25/04/2011 20:02	2326,4
15.0 GB free on volume

Next day:

Name	AccessTimeDT	Total
exchsnap__ecorreo__recent	23/05/2011 20:02	1264,1
exchsnap__ecorreo_05-22-2011_22.01.19__daily	22/05/2011 20:02	2713,7
exchsnap__ecorreo_05-21-2011_22.01.24__daily	21/05/2011 20:02	875,7
exchsnap__ecorreo_05-20-2011_22.02.22__daily	20/05/2011 20:03	1628,9
exchsnap__ecorreo_05-19-2011_22.02.14__daily	19/05/2011 20:03	3076,2
exchsnap__ecorreo_05-18-2011_22.02.10__daily	18/05/2011 20:02	2675,6
exchsnap__ecorreo_05-17-2011_22.01.21__daily	17/05/2011 20:02	2882,9
exchsnap__ecorreo_05-16-2011_22.35.32__daily	16/05/2011 20:36	2972,3
exchsnap__ecorreo_05-15-2011_22.02.05__daily	15/05/2011 20:02	2054,8
exchsnap__ecorreo_05-14-2011_22.02.25__daily	14/05/2011 20:03	1308,2
exchsnap__ecorreo_05-13-2011_22.01.20__daily	13/05/2011 20:02	2243,1
exchsnap__ecorreo_05-12-2011_22.01.20__daily	12/05/2011 20:02	1990,5
exchsnap__ecorreo_05-11-2011_22.01.19__daily	11/05/2011 20:02	2144,1
exchsnap__ecorreo_05-10-2011_22.01.16__daily	10/05/2011 20:01	3123,4
exchsnap__ecorreo_05-09-2011_22.01.17__daily	09/05/2011 20:01	2522,1
exchsnap__ecorreo_05-08-2011_22.01.20__daily	08/05/2011 20:02	2668,2
exchsnap__ecorreo_05-07-2011_22.01.22__daily	07/05/2011 20:02	1598,2
exchsnap__ecorreo_05-06-2011_22.01.19__daily	06/05/2011 20:02	2251,7
exchsnap__ecorreo_05-05-2011_22.01.21__daily	05/05/2011 20:02	3889
exchsnap__ecorreo_05-04-2011_22.01.20__daily	04/05/2011 20:02	2987,9
34.0 GB free on volume

With an increment of 2.9 GB, snapshots are deleted about 15 GB. The volume had 15 GB of free space.

Is working wrong DATA ONTAP??

Darkstar · ‎2011-05-31

This is the correct behaviour.

You say you want Autodelete to free up 20% in your volume. Your volume is 180gb. 20% of 180gb is ~36gb. So snap autodelete deletes until 36gb are free. If you have "only" 34gb free, it means that autodelete actually stopped too early, it should have deleted one more snapshot to reach 36gb free space 😉

If you want to delete fewer snapshots, simply set the target_free_space option lower. You shouldn't set it below 10gb though, as that is the minimum "target_free_space" value for a volume of that size. So if you set target_free_space to 10% (the minimum), you will make autodelete free up only ~18gb on the volume. You cannot, however, control the point where Autodelete starts. For a volume of 180g it always starts when the volume is 92% full and deletes untill target_free_space percent are free.

Hope that helps

-Michael

View solution in original post

Darkstar · ‎2011-05-31

This is the correct behaviour.

You say you want Autodelete to free up 20% in your volume. Your volume is 180gb. 20% of 180gb is ~36gb. So snap autodelete deletes until 36gb are free. If you have "only" 34gb free, it means that autodelete actually stopped too early, it should have deleted one more snapshot to reach 36gb free space 😉

If you want to delete fewer snapshots, simply set the target_free_space option lower. You shouldn't set it below 10gb though, as that is the minimum "target_free_space" value for a volume of that size. So if you set target_free_space to 10% (the minimum), you will make autodelete free up only ~18gb on the volume. You cannot, however, control the point where Autodelete starts. For a volume of 180g it always starts when the volume is 92% full and deletes untill target_free_space percent are free.

Hope that helps

-Michael

cheche030 · ‎2011-05-31

Thanks Michael,

I think that I had made wrong my calculations. This behavior is all right.